COVID-19 EXPRESS PCR TEST: IN CLINIC BY A MEDICAL PROFESSIONAL (CURRENT INFECTION STATUS)

Also known as an Antigen test, it detects the presence of viral RNA. It aims to answer: do I have the virus now? This requires taking a swab from the throat and nose and then analysing the specimen in the lab using the polymerase chain reaction (PCR).

The test is taken to:
⦁ Diagnose infection
⦁ Test following infection to see if the virus has been cleared
⦁ Screen asymptomatic individuals to detect if they carry virus and are potentially infectious

Antigen tests are a crucial part of mitigating transmission as we come out of lockdown. We need the ability to detect the carriage of covid-19 and respond to it rapidly. As people return to work and society tentatively re-opens, robust testing programmes as part of a return to work strategy will be key to reduce spread and improve confidence amongst employees and customers

These tests are currently widely used for travel where the airline or destination country requires a negative result and certificate within specified time periods. Organisations are also using these tests to screen employees so they can safely return to their place of work.

Results are available 90 minutes after your appointment time.

We have a number of partner laboratories we work with. We only use laboratories with the highest accreditation standards, such as UKAS approved laboratories accredited to ISO 15189.

The testing method for 2019-nCoV Coronavirus Covid-19 is a molecular assay based on the detection of the nucleic material (RNA) within the virus.  Whereas other testing methods are based on the detection of antibodies which are only produced as a response to the infection, detection of viral RNA allows for the identification of an infection at a much earlier stage after an initial exposure. If your test comes back positive, you will need to follow the NHS guidance on self-isolation. Our lab will be able to confirm the variant of Covid-19 that you tested positive for within 5 days of your positive result (on request).

The test has a minimum Sensitivity of 98% and a Specificity of 100%.

Sensitivity concerns the false negative rate and is expressed as a percentage: out of 100 truly positive patients, how many are detected as positive by the test? The higher the sensitivity, the fewer the numbers of false negatives. In the USA, sensitivity is often called positive percent agreement (PPA). 

Specificity concerns the false positive rate and is expressed as a percentage: out of 100 truly negative patients, how many are detected as negative by the test? The higher the specificity, the fewer the numbers of false positives. An example here would be if the test detects an antibody response to a different but related coronavirus. The individual would be informed that they have antibodies to covid-19 when in fact it would reflect infection with a different but similar coronavirus. In the USA, specificity is often called negative percent agreement (NPA). 

We also need to interpret the test results in context. The likelihood of a true positive or true negative will vary depending on the prevalence-how common the condition is within a population. For covid-19, we can estimate but these are not firm yet. This is explained in a great article here.

Before taking the test, it is important to understand the following.

1. Do not use any nasal medication or mouthwash for at least 24 hours prior to testing. This can spoil the sample.
2. Do not chew gum, drink coffee or smoke for at least 2 hours prior to testing. This may spoil the sample.
3. Laboratory capacity, test re-runs or inconclusive results can cause delays. If an inconclusive result is returned, a brand-new collection is required.
4. You need to be aware of the above and make an informed decision to proceed, particularly if you have time constraints for international travel.